This is why I discovered my original Naniwa set was convex! They just seemed to stop working properly, so I did what seemed reasonable - I got out my Shapton DGLP and started to take off the top layer, which resulted in elliptical areas of newly exposed substrate being exposed in the middle of each hone, and which slowly grew as I worked away. The sad thing was that those hones never worked very well after that, yet I remembered them working extremely well before I lapped away that top layer. Maybe my response was over the top, but I bought a whole new set (SRD probably liked that!) and they worked as expected. I have refrained from lapping the new set in any way.
It appears to me from my limited experience that lapping these hones with a diamond plate changes the remaining exposed surface into something smooth that declines to cut. Were I to do it again, I'd probably try to lap each with the Naniwa below it (3k with 1k, 5k with 3k etc). I may be wrong about all of this, but there is something going on that makes these man-made ceramics not behave as they did when sold after having their surfaces altered. You may think you are refreshing them, but you end up altering them. Great hones, but beware of this. As I said, I might be quite wrong in generalising my experience to all, but that's what happened to me.
